1. Field of the Invention
The present invention relates to an IC card which can be suitably used in various fields of a finance/settlement field, a public utility field, a communication/broadcasting field, a transportation/traffic field, a distribution/retail service field, and an ID field, of which handling is easy, and of which information can be visually recognized. The present invention also relates to a method of operating an IC card.
2. Description of the Related Art
Recently, research and development of an IC card is actively being made. The IC card is generally formed by mounting an IC chip or the like, which is capable of storing information, on a plastic card having a size of credit card. Since the IC card has excellent portability, high function, and high performance, application of the IC card is being examined in various fields. The IC card is divided into a contact IC card and a contactless IC card. The contact IC card is designed to come into electric contact with a terminal such as a reader/writer to receive power and transmit/receive data to/from the terminal. The contactless IC card is designed to receive power by using electromagnetic waves and so as to be able to transmit/receive data to/from a terminal such as a reader/writer without electric contact.
In the IC card, desirably, stored information such as information of a use state (whether the IC card is unused or in use, a used rate, a remaining amount, and the like) can be easily recognized.
Hitherto, as known by a telephone card, a prepaid card, and the like, the information such as the use state is recorded by punching, thermal recording using a photosensitive recording material, and the like.
In any of the cases, however, a terminal is required to equip a special function such as a punching function or a heating function, moreover, the terminal and a card have to come into contact with each other. Since any of the cards does not have a display portion, in order to check the information such as a use state, the user has to go to a station or a commercial facility where a card reader installed or has to have a personal card reader.
Hitherto, a method of assembling a liquid crystal display in the IC card and using a supporting member for reinforcement so as to have bending strength is proposed in, for example, Japanese Patent Application Laid-Open (JP-A) No. 2001-283176 and the like.
In this case, however, the method has the following problems:
                (1) It is necessary to equip a power supply source such as a battery in the IC card.        (2) Since the liquid crystal display, the battery, and the like need to be deposed within the IC card standard thickness of 0.76 mm, it is difficult to design assembly of the aforementioned parts with such a limited space.        (3) When assembly of the liquid crystal display, the battery, and the like is facilitated, disassembly becomes easy. If disassembly is easy, even internal analysis becomes easy, so that the card is easily forged.        (4) As the manufacturing process is complicated, the cost increases.        
Conventionally, a method of assembling an electrochromic display device using a viologen compound is proposed in, for example, JP-A No. 11-232412 and the like. In this case, however, information on a display is maintained only when a low voltage is applied to the display. There is hence a problem of maintaining the information on the display after the voltage is stopped applying. Further, a method of assembling an electrochromic display device using a compound having a triphenylmethane structure in the IC card is proposed in JP-A No. 2000-322549 and the like. In this case, however, an aqueous electrolyte is necessary, so that manufacture of the IC card or the like is complicated and there are problems such as leakage of the liquid and breakage at the time of using the IC card and the like, and spread of the electrolyte liquid when the IC card and the like is discarded.